What would the appearance of gram pos and neg bacteria be if

What would the appearance of gram pos and neg bacteria be if:

a. you forgot to counterstain with safranin

b. the mordant (iodine) were not used

c. the decolonizing step was omitted

d. the decolonizing step was too long?

Solution

a. If we forget to counterstain the inoculum, we will not be able to identify gram negative bacteria. Because garm positive bacteria are only able to stain with crystal violet dye which is applied to the inoculum before safranin.Due to the presence of thin peptidoglycan, gram negative bacteria absorb crystal violet but during decolorizing step, itremoves the violet stain.

b. The funcion of iodine is to hold cyrstal violet dye to the applied surface. It means if iodine solution is not given to the cell, the crystal violet dye will be washed off after applying ethanol.

c. If decolorizing step is omitted, we will not be able to identify gram positive and gram negative bacteria because both the form will appear in violet color.

d. The purpose of decolorization is to make te cell wall or membrane porous and remove the stain. If the decolorizing step take long time, then it is possible that the cell wall and cell membrane gets rupture and the cell would lose its original structure.